Known as representative prior art techniques for producing an aromatic polycarbonate are processes in which 2,2-bis(4-hydroxyphenyl)propane (hereinafter abbreviated as bisphenol A) is reacted with a compound capable of incorporating a carbonate bond, such as phosgene or a carbonic diester. Of those processes, a transesterification process has advantages in operation and cost over a phosgene process (interfacial polymerization process) because the steps thereof are relatively simple. In addition, the transesterification process has recently come to be thought better of from the standpoint of environmental protection, because neither phosgene, which is highly toxic, nor a halogenated solvent, e.g., methylene chloride, is used in the process.
However, practical use of the transesterification process for large-scale industrial production is still limited because it has some drawbacks over the phosgene process concerning polycarbonate properties and the process itself. In particular, a serious problem concerning properties of the polycarbonate obtained by the transesterification process is that the hue of the polycarbonate deteriorates upon heating.
Various investigations have been made so far in order to overcome the above problem. Examples thereof include addition of an acidic compound and an epoxy compound (see JP-A-4-175368; the term "JP-A" as used herein means an "unexamined published Japanese patent application"), addition of a phosphite compound (see JP-A-3-265625), and addition of a hindered phenol compound (see JP-A-4-41525). However, even with the incorporation of these additives into a polycarbonate, it has still been difficult to obtain a polycarbonate composition having sufficient thermal stability.